Loud-speaker



July 28, 1942. s p, FQLTZ E L I 2,291,459

LOUD SPEAKER Filed June 8, 1940 F/QZ 57W4RTPfZ7L7Z ffhmo/vo 5. PE TERSONINVENTOR 5 ATTORNEY Patented July 28, 1942 OFFICE LOUD-SPEAKER StewartP. Foltz and Raymond B. Peterson, New Castle, Pa.

Application June 8, 1940, Serial No. 339,514

3 Claims.

This invention relates to voice amplifying or reproducing equipment,and, more particularly, is concerned with an apparatus of the loudspeaker type operated by compressed air or other fluid.

Heretofore, it has been proposed to provide a loud speaker in whichcompressed air is employed to produce the sound waves by controlling theescape of compressed air by electrical means actuated by electricalimpulses controlled by sound waves. For example, a valve has been usedto control the escape of compressed air to a loud speaker horn and thevalve is controlled by magnetic means responsive to the electricalimpulses generated in a microphone or an electrical pickup with orwithout amplification by a vacuum tube system. We have found, however,that the usual magnetic means for controlling the opening and closing ofthe compressed air valve are not sufficiently rapid or sufificientlyresponsive of a wide range of frequencies to effect a fine tone qualityof reproduction of the sound. Also, we have found that known apparatusis relatively complicated in construction, expensive to manufacture,delicate in adjustment and maintenance and possesses undesirable,inherent damping characteristics.

It is the general object of our invention to avoid and overcome theforegoing difficulties of known pneumatic loud speakers by the provisionof a relatively inexpensive, simple, rugged, undamped and easilyadjusted compressed air speaker which is characterized by extremely highquality reproduction and wide frequency response range.

Another object of our invention is the provision of a piezo-electricalcontrol for a compressed air loud speaker.

Another object of our invention is to provide a pneumatically-balancedvalve for controlling the flow of compressed air to a loud speaker hornwhich valve has a light-weight, rotatable, closure member moved to theopen and closed position by piezo-electric means.

Another object of our invention is the provision of an improved mountingfor this piezoelectrical means whereby it is adapted for oscillationabout an axis of rotation.

Another object of our invention is to provide a piezo-electric crystalmounted for oscillation about a given axis and adapted to open and closea valve connected directly to the oscillating portion of the crystal.

Another object of our invention is to provide an improved pneumaticallyoperated loud speaker.

The foregoing and other objects of our invention are achieved by theprovision of a valve adapted to be connected to a source of air underpressure, a pneumatic-balanced rotary plug in the valve, andpiezo-electrical means connected to oscillate the plug and open thevalve greater and less amounts upon activation of the piezoelectricalmeans by sound controlled electrical impulses.

For a better understanding of our invention reference should be had tothe accompanying drawing wherein Fig. 1 is a longitudinal crosssectionalview through an apparatus embodying the principles of our invention;Fig. 2 is a transverse cross-sectional view taken on line IIII of Fig.1; Fig. 3 is a fragmentary cross-sectional view taken on line IIIIII ofFig. 1; and Fig. 4 is a fragmentary cross-sectional view taken on lineIVIV of Fig. 1.

In the drawing, the numeral I0 indicates, as a whole, a cylindricalhousing having a removable end plate I2 secured thereto, as by screwsHi. The end plate I2 and the housing II] are formed with a central oraxial bore which snugly receives a tube IS. The ends of the tube I6engage in sealing relation with the housing Ill and the end plate I2 butthe center portion of the tube is surrounded by the chamber I8 in thehousing which chamber is adapted to be connected to a source of gas orfluid, as for example air, by means not shown. The housing I0 isprovided with a circular flange 20 which is adapted to have the smallend of a 101"... speaker horn, or the like, secured thereto so that thehorn will be positioned axially of the tube I6.

Suitable means are provided for holding the tube I6 in position and foralso allowing a slight rotatable adjustment of the tube. For thispurpose, one end of the tube I6 is formed with a flange 22 which engageswith the outer surface of the end plate I2. A portion of the flange 22is thickened and cut with an arcuate rack, as at 24, which engages witha worm or screw 25 out or mounted on a shaft 26 journaled at its ends ina laterally extended flange 2'! usually made integral with the end plateI2. A knurled knob 28 secured to the shaft 26 provides for the rotationof the shaft, and a spring finger 30, holds the knob 28, shaft 26, andtube I6 against rotation. The spring finger 3B is mounted on a cover 32,usually of streamline shape, which is fastened to the housing III.

The tube I6 is formed with a plurality of circumferentially-spaced,longitudinally-extending slits or ports as more fully described andclaimed in the co-pending application of Edward F. Chandler, Serial No.310,361.

Rotatably received within the tube I6 is a thin-walled cup or plug 36 oflight weight material slightly shorter in length than the length of thetube I6. The cup 36 is ordinarily made of duralumin or other relativelystrong, hard, light-weight material and is provided with a plurality ofcircumferentially-spaced, longitudithe stud 42.

2 3,201,459 r i I a is just cut oil. With the valve portion of the ap- Vnally-extending slits or ports a which are adaptedto be moved into andout or register with the ports or slits formed in the tube I. Ob-'viously. when the slits in the cup II are completelyin register with theslits in the tube II. a large volume of air is passed from the chamberI. out through the flange II and into the speaker horn. However, whenthe slits ll oi the cup It are not in register with the slits in thetube It substantially no air escapes from the chamber is. The cup 86 maybe. provided with small circumterentially continuous a sealing groovesor means II at either end of the slits II.

The bottom 01' the cup is positioned at the end of the tube it adjacentthe flange 22 and the cup terminates in a stud-portion 42 which isaxially aligned with the axis of the cup and tube.

As best shown in Figs. 1, 3 and 4, piezo-electric means areincorporatedwith the valve mechanism heretofore described to produce and control theoperation of the valve. In the apparatus illustrated, thepiezo-electrical means includes a substantially rectangular housingmember 46 formed in upper and'lower parts and terminating in a right'angle flange 48 which is secured as by screws 48 to the circular flange28. The rectangular housing 46 is formed with a rectangular aperture I.through its center which is in alignment with the stud 42 formed on theend of the cup I. A piezo-electrlcal crystal 52 usually of flatrectangular shape, is carried in the aperture 50 oi the housing memberll so as to be in spaced relation to the side, top and bottom walls ofthe aperture 50.

paratus in this condition electrical impulsesoppllcdtothepiezo-electricalcrystall! causesitto oscillate about itscentral axis which oscillations act through the direct coupling means IIand I2 tooscillatethecupflandbringtheslitsorports ll of the cup into andout or register with the ports and slits in the tube It; Thus,- greaterand lesser amounts-oi airare permitted to escape from the chamber is outthrough the speaker horn connected to the flange 20. The result is avery loud sound amplification oi the original I sound waves, reproducedover a particularly wide frequency range and at high quality.

18 From the foregoing it will be 'evident'that the objects of ourinvention have been achieved by the provision of relatively inexpensiveapparatus employing a plead-electrical crystal to control a pneumatictype loud speaker. The improved loud 20 speaker 01 our inventionisexceptionally rugged and can be used under various conditions oftemperature and pressure with little or no adjustment. The apparatus canbe used over long periods without repair and it it should become necgsessary to provide a new crystal the installation thereo! is a simplematter. The valve portion of the apparatus is pneumatically balancedinasmuch as the air pressure acts equally on all sides *of the cup andas a result the cup 36 is readily 80 oscillated by the crystal 52 whichis connected di- 7 rectly thereto.

While in accordance with the Patent Statuteswe have specificallyillustrated and described our advance in the art, it should beunderstood that The plaza-electrical crystal is mounted so that we arenot limited thereto or thereby but that it will be free to oscillatearound a suitable axis,-

trally of the crystal adjacent the end thereof closest to the cup 38.The result is that the piezo crystal 52 is resiliently mounted forsubstantially free oscillation movement around an' axis, and

specifically a central axis. Ordinarily, the resilient means arecompressed but slightly in mounting the crystal therebetween.

The end of the piezo-crystal adjacent the stud 42 is secured, as bycement, to a channelshaped coupling'melnber 60 which has acup 62 formedthereon which cup surrounds the stud l2 and to whichthe stud may besecured by a suitable cement. The piezo crystal '52 may. be electricallyconnected to binding posts 54 mounted on the cover 32 and electricallyinsulated therefrom.

It is believed that the operation of our improved I pneumaticloudspeaker will be evident from the foregoing description. However,briefly reviewing the operation, the apparatus is connected to a sourceof compressed air, an amplifying horn is mounted on the flange 20, andan amplifier is connected to the binding posts it. Then the knob 28 isadjusted for any given condition so that without electric currentflowing to the binding posts 54 there is no escape of air from thechamber it through the slits in the tube It and the slits 38. Usually,the knob 28 is turned to first align the ports 38 inthe cup 36 with theports in the tube so that there is an escape of air. Thereafter, theknob is turned until the escape of the scope of our invention is definedin the appendedclaims. I

We claim: l. A pneumatic loud speaker comprising a tube,

40 a housing providing-an air chamber at least partially, around thetube intermediate the ends thereof, a light weight cup received snuglywithin the tube, said cup and tube having ports adapted to be moved intoand out of register upon rotation of the cup about its axis, aplaza-electrical crystal mounted at the closed end of the cup so thatthe axis oi the cup'passes through the plane of the crystal, the edgeoithe crystal remote from the cup being mounted resiliently oversubstantially mg full width of the crystal and at right angles tothe cupaxis, the end of the crystal adjacent the cup being resiliently mountedonly at a laterally-narrow, central area, and means connecting theadjacent end of the crystal to the cup.

2. In combination. a rotary valve for controlling the flow of fluid, apiezo-electrical crystal, means mounting. the crystal for oscillationadlament the valve and so that the axis 01 the valve passes through theplane of the crystal, and means 00' connecting the crystal to the valveso that oscillations of the crystal will open the valve to greater andless amounts.

3. In combination, a rotary valve for controlling the flow of fluid,said valve being balanced,

in a radial direction at all times during its control of fluid flow, apiezo-electrical crystal, means mounting the crystal for oscillationadjacent the valve and so that the axis of the valve passes through theplane of the crystal, and means con- 7 necting the-crystal to the valveso that oscfllations of the crystal will open the valve to greater andless amounts.

STEWART P. FOLTZ. RAYMOND B. PETERSON.

